Boron isotope variations in the atmosphere

Abstract

We report here the first measurements of boron isotope ratios in the maritime atmosphere together with those of precipitation. The δ11B values of atmospheric condensates in the western North Pacific and Japanese coast and snow in Tokyo range from -12.8 to +5.1‰ and from -0.4 to +0.4‰, respectively, which are significantly lower than those of rainwater (+18.9 to +34.7‰) collected mostly over the North Pacific. Since the ¹¹B/¹⁰B ratios of the atmosphere are lower than those of volcanic emissions (δ¹¹B=+2.3 to +21.4‰), we must seek sources for atmospheric boron other than volcanism. We postulate that the sea may be an important supplier for atmospheric boron under some dynamic conditions and that boron isotope fractionation during evaporation from seawater and removal from the atmosphere may account for the large variations of ¹¹B/¹⁰B ratios observed in the atmosphere and precipitation.